数轴上点A表示-3,点B表示1,则表示A、B两点间的距离的算式是[ ]
A.-3+1
B.-3-1
C.1-(-3)
D.1-3
答案:C
一Look! That teacher is explaining something to her students again and again!
一_______teacher she is!
A.How patient
B.What patient
C.How a patient
D.What a patient
治疗前后覆盖覆抬改善的机制主要是
A.上颌前牙的压低B.上颌磨牙的伸长C.因下颌的前下方向生长改善了覆盖D.上颌前牙的伸长E.上颌前牙的压低、上颌磨牙的伸长以及下颌的前下方向生长共同所致